The present invention relates to dental operatories and in particular to vacuum disposal systems for removing waste from the oral cavity during dental operations. The invention is disclosed in alternative preferred configurations of water recycling and waste disposal system for dental operatories.
In the course of dental procedures such as drilling and filling or polishing teeth, conventional dental operatories provide for continuing evacuation from a patient's mouth of effluent containing saliva, water, pumice, amalgam, tooth chips, body tissue, and nitrous oxide when used in particular dental procedures. The operatory includes a vacuum tube placed in the patient's mouth to remove effluent as it is generated during the course of a procedure to a collection and disposal point within the dental office. The operating vacuum is produced by a water seal vacuum pump which requires a substantial water volume to maintain the pump seal in continuous operation throughout dental office hours. In an effort to reduce water consumption by the vacuum pump, conventional systems separate "gray water" from patient effluent and recycle the gray water to provide water sealing for the vacuum pump. Solids are screened from the effluent before entering the vacuum pump to provide a supply of gray water, and excess gray water is discharged to a disposal drain. A system of this kind includes a make-up water supply to augment the gray water supply so as to assure a proper water seal at all times for the operating vacuum pump. Water consumption of the vacuum system is determined by the volume of fresh make-up water required by the system on an hourly or daily basis.
U.S. Pat. No. 4,344,756 to Folkenroth et al. discloses a water recycler for dental operatories in which gray water from several office operatories is directed via a solids collector go the inlet side of twin vacuum pumps operating in parallel. The gray water is discharged from the vacuum pumps to a gas-water separator which functions also as a gray water reservoir. From the separator air is vented to atmosphere, gray water is recycled to the vacuum pump inlet, and excess gray water is discarded to a plumbing drain. A fresh water make-up feed system is operated intermittently to maintain the gray water reservoir at a prescribed level, and if necessary, to supply fresh water directly to the inlet side of the vacuum pumps.
U.S. Pat. No. 5,032,260 to Alzner discloses a system somewhat similar to Folkenroth for recycling gray water to provide a water seal for a dental operatory vacuum pump. In Alzner, gray water from the operatory passes a solids filter, enters the inlet of the vacuum pump and exits into a gas-liquid-solids separator. The gray water is recycled by means of a fresh water eductor which induces gray water flow from the separator into a commingled stream of gray/fresh sealing water. In an example of the invention, Alzner discloses fresh water usage of approximately 1/8 gpm or 7.5 gallons per hour.
The gas-liquids-solids separator disclosed in Alzner has an interior layout designed for minimizing the transfer of heat from the entrained gas to separated gray water so as to minimize unwanted increase in the vapor pressure of recycled water, a condition that is detrimental to optimum performance of the vacuum pump. Alzner also uses a greater amount of fresh water to make the eductor operate properly and to maintain the temperature of commingled sealing water at a suitable level for optimum vacuum pump performance.
Both of these patented systems rely on filters and separators to screen out solids and gas from operatory effluent to produce gray water as clean as possible. The filters and separators are effective to screen out larger particles such as amalgam and tooth chips, however, finer abrasive particles as well as tooth cleaning pumice are likely to pass through the filter along with the gray water recycling through the system and cause wear of vacuum pump water seals, impeller, and housing.
The emphasis in both Folkenroth and Alzner is to recover and recycle gray water for use as pump seal water. Both patents simply provide a solids filter or collector immediately before operatory effluent enters the vacuum pump. Screens or filters of very fine mesh adequate to screen out pumice from operatory effluent are prone to clogging thereby diminishing the efficiency of the vacuum system. To avoid loss of efficiency, larger mesh screens are selected to filter out larger solids, principally tooth chips and amalgam, while a significant portion of pumice is carried along with gray water through the screen into water pump seals. Pumice consists chiefly of silicates of aluminum, potassium, and sodium and abrades vacuum pump components gradually diminishing pump capacity. Accordingly, gray water recycling while improving water conservation does nonetheless less entail the disadvantage of increased vacuum pump wear.
European Patent No. 284,641 to Alkirk is of interest in pointing out that amalgam and other harmful metal compounds (mercury, silver, and tin) from dental surgeries require separation from mouth rinsing water for recovery of the heavy metals. Alkirk discloses such a system for separation and recovery.
The prior art includes other devices and techniques for separating and disposing of dental operatory effluent by using suction systems. These are U.S. Pat. Nos. 2,784,717 to Thompson, 2,821,021 to Winter, 3,988,134 to Gandrud, and 4,293,300 to Cattani. These patents are directed to maintaining system suction while separating and disposing of liquid and solid components of operatory effluent.
A suitable system for disposing of dental operatory effluent is characterized by low water consumption for a water seal vacuum pump through the recycling of seal water, means for controlling the temperature and vapor pressure of recirculating seal water, avoiding the presence of abrasives in seal water and consequential pump wear, reliable separation and disposal of gas-liquid-solid constituents of operatory effluent, collection and recovery of amalgam and heavy metals, and means for disinfecting the effluent. These matters are the subject of the present invention.